[PATCH v2 3/4] powerpc/watchdog: avoid sys_info fallback for all_bt

[Bradley Morgan <include@grrlz.net>]

The powerpc watchdog prints all CPU backtraces itself. When the watchdog
mask contains only SYS_INFO_ALL_BT, stripping that bit leaves zero and
sys_info(0) falls back to kernel_sys_info.

Use sys_info_without_all_bt() so an explicit all_bt mask does not request
the global default.

Fixes: e561383a39ed ("powerpc/watchdog: add support for hardlockup_sys_info sysctl")
Cc: stable@vger.kernel.org
Signed-off-by: Bradley Morgan <include@grrlz.net>
---
Changes since v1:
- Use the shared sys_info_without_all_bt() helper.
- Keep the powerpc watchdog change in its own patch.

 arch/powerpc/kernel/watchdog.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/kernel/watchdog.c b/arch/powerpc/kernel/watchdog.c
index c40c69368476..813f9d48a6be 100644
--- a/arch/powerpc/kernel/watchdog.c
+++ b/arch/powerpc/kernel/watchdog.c
@@ -201,6 +201,7 @@ static bool set_cpu_stuck(int cpu)
 static void watchdog_smp_panic(int cpu)
 {
 	static cpumask_t wd_smp_cpus_ipi; // protected by reporting
+	unsigned long si_mask;
 	unsigned long flags;
 	u64 tb, last_reset;
 	int c;
@@ -236,8 +237,9 @@ static void watchdog_smp_panic(int cpu)
 	pr_emerg("CPU %d TB:%lld, last SMP heartbeat TB:%lld (%lldms ago)\n",
 		 cpu, tb, last_reset, tb_to_ns(tb - last_reset) / 1000000);
 
+	si_mask = READ_ONCE(hardlockup_si_mask);
 	if (sysctl_hardlockup_all_cpu_backtrace ||
-	    (hardlockup_si_mask & SYS_INFO_ALL_BT)) {
+	    (si_mask & SYS_INFO_ALL_BT)) {
 		trigger_allbutcpu_cpu_backtrace(cpu);
 		cpumask_clear(&wd_smp_cpus_ipi);
 	} else {
@@ -251,7 +253,7 @@ static void watchdog_smp_panic(int cpu)
 		}
 	}
 
-	sys_info(hardlockup_si_mask & ~SYS_INFO_ALL_BT);
+	sys_info_without_all_bt(si_mask);
 	if (hardlockup_panic)
 		nmi_panic(NULL, "Hard LOCKUP");
 
@@ -371,6 +373,7 @@ static void watchdog_timer_interrupt(int cpu)
 
 DEFINE_INTERRUPT_HANDLER_NMI(soft_nmi_interrupt)
 {
+	unsigned long si_mask;
 	unsigned long flags;
 	int cpu = raw_smp_processor_id();
 	u64 tb;
@@ -418,11 +421,12 @@ DEFINE_INTERRUPT_HANDLER_NMI(soft_nmi_interrupt)
 
 		xchg(&__wd_nmi_output, 1); // see wd_lockup_ipi
 
+		si_mask = READ_ONCE(hardlockup_si_mask);
 		if (sysctl_hardlockup_all_cpu_backtrace ||
-		    (hardlockup_si_mask & SYS_INFO_ALL_BT))
+		    (si_mask & SYS_INFO_ALL_BT))
 			trigger_allbutcpu_cpu_backtrace(cpu);
 
-		sys_info(hardlockup_si_mask & ~SYS_INFO_ALL_BT);
+		sys_info_without_all_bt(si_mask);
 		if (hardlockup_panic)
 			nmi_panic(regs, "Hard LOCKUP");
 
-- 
2.53.0